To detect leakage beyond a metering point, utilities currently have to deploy an expensive data recorder to monitor intervals over a time period of interest. The data recorded is left in place, logging water consumption over a series of short intervals (on the order of 5 minutes). Post analysis of the data recorder looks for the minimum consumption level with the theory that at least one interval will register zero consumption if there are no leaks. If there are leaks, there will not be a zero level. In this model, the data recorder is too expensive to leave at the site and must be portable and moved to where a perceived leak may be.
Some AMR providers support leak detection, but in a brute force, non-efficient manner. These devices can be used to record the full interval data, but at added device, communications, and operations cost. Additional memory is needed to store essentially a month's worth of 5 minutes of data, communicating this amount of interval data is not possible by today's technology models for the industry—only a warning flag can be sent. Thus, there is an operations cost that is incurred in responding to the warning flag via a service call to manually collect the full interval data. This is troublesome, because the leak may be inconsequential or it may be a flood. In either case, the leak detection system will respond with the same level of priority.
In one approach, a utility company uses expensive (e.g., $2,500 FS Brainard) data recorders to detect water leakage in a seemingly unconventional, but effective manner. The data loggers are initially set to record hourly consumption. If a leak is suspected they are then programmed to record 10-second consumption. The theory is that there must be at least one interval where there is no water consumption: an interval that registers ‘0’ units of water usage. If there is no such interval, the conclusion is that there is a water leak in the system. Using this approach helped the utility company to identify a 6 gallon/minute, $700 per month leak at a local hospital.
Other examples of leak detection systems are described in U.S. Pat. Nos. 5,155,481, 5,617,084 and 6,181,257, however they are not without their shortcomings. For instance, the '481 patent to Brennan, Jr. et al., discloses the use of a reed switch in combination with the magnetically coupled drive of the water meter. This approach is subject to failure over time since the state of the reed switch (or any other similar mechanical element) must be determined and such devices are subject to failure from fatigue. With respect to the '084 patent to Sears, only a yes/no indication of a leak is provided without an actual value of leakage level that would be of assistance to the user.
The trend of water becoming a less abundant resource, combined with the fact that utility companies are realizing that they are experiencing as much as 20% water leakage losses, highlights the need for finding a water leak detection system that is easy to implement and that requires a lower expenditure to implement.